Ascorbic acid is a safe and useful antioxidant, and is known as a compound having an excellent whitening effect. On the other hand, it is unstable against light, heat and oxidation, suitably utilization thereof in the cosmetic field is prevented. Then, various ascorbic acid derivatives or salts thereof are suggested as materials having improved stability over time in comparison with ascorbic acid, and it is suggested to compound them into a skin external agent for whitening (patent document 1, patent document 2) and to compound them into a cosmetic (patent document 3).
However, many of the above-described ascorbic acid derivatives and salts thereof have problems such as coloration and generation of odor over time and the like, and the stability over time thereof is still insufficient. Moreover, endurance of activity in a living body is short. Thus, there is a desire for improvement thereof.
As materials further improving stability over time, an ascorbic acid phosphate and ascorbic acid glucoside generating free ascorbic acid by the action of an enzyme and the like are suggested (patent document 4). However, the production of them is complicated and they are expensive. Then, an ascorbic acid derivative is desired which has excellent functions originally owned by ascorbic acid derivatives such as a whitening effect, collagen production promoting effect and the like, shows stability over time, and further, can be produced by an inexpensive and simple production method.    (Patent document 1) JP-A No. 62-221611    (Patent document 2) JP-A No. 2005-60239    (Patent document 3) JP-A No. 1-228978    (Patent document 4) Japanese Patent No. 2926412